First character help

Hey guys, i'm new to poe this league. I leveled my glad molten strike and i recently re-spec'd to double strike and followed mathils guide. My damage is consistent but I feel like a glass cannon, I'm getting deleted by some bosses and syndicate members on tier 9 maps. I could use some advice on what to fix. I have a feeling its low HP, I just want some advice before i start blowing currency. Thanks!